linux-kernel - Forwarded: [PATCH] net: usb: asix: validate PHY address before use

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Message-ID: <69424d5e.a70a0220.25eec0.0016.GAE@google.com>
Date: Tue, 16 Dec 2025 22:27:42 -0800
From: syzbot <syzbot+3d43c9066a5b54902232@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Forwarded: [PATCH] net: usb: asix: validate PHY address before use

For archival purposes, forwarding an incoming command email to
linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com.

***

Subject: [PATCH] net: usb: asix: validate PHY address before use
Author: kartikey406@...il.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master


The ASIX driver reads the PHY address from the USB device via
asix_read_phy_addr(). A malicious or faulty device can return an
invalid address (>= PHY_MAX_ADDR), which causes a warning in
mdiobus_get_phy():

  addr 207 out of range
  WARNING: drivers/net/phy/mdio_bus.c:76

Validate the PHY address before returning it from asix_read_phy_addr().

Reported-by: syzbot+3d43c9066a5b54902232@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=3d43c9066a5b54902232
Fixes: 7e88b11a862a ("net: usb: asix: refactor asix_read_phy_addr() and handle errors on return")
Signed-off-by: Deepanshu Kartikey <kartikey406@...il.com>
---
 drivers/net/usb/asix_common.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c
index 7fd763917ae2..6ab3486072cb 100644
--- a/drivers/net/usb/asix_common.c
+++ b/drivers/net/usb/asix_common.c
@@ -335,6 +335,11 @@ int asix_read_phy_addr(struct usbnet *dev, bool internal)
 	offset = (internal ? 1 : 0);
 	ret = buf[offset];
 
+	if (ret >= PHY_MAX_ADDR) {
+		netdev_err(dev->net, "invalid PHY address: %d\n", ret);
+		return -ENODEV;
+	}
+
 	netdev_dbg(dev->net, "%s PHY address 0x%x\n",
 		   internal ? "internal" : "external", ret);
 
-- 
2.43.0